As a related-art stacking-type header, there is known a stacking-type header including a first plate-shaped unit having a plurality of outlet flow passages formed therein, and a second plate-shaped unit stacked on the first plate-shaped unit and having a distribution flow passage formed therein, for distributing refrigerant, which passes through an inlet flow passage to flow into the second plate-shaped unit, to the plurality of outlet flow passages formed in the first plate-shaped unit to cause the refrigerant to flow out from the second plate-shaped unit. The distribution flow passage includes a branching flow passage having a plurality of grooves extending perpendicular to a refrigerant inflow direction. The refrigerant passing through the inlet flow passage passes through the plurality of grooves to be branched into a plurality of flows, to thereby pass through the plurality of outlet flow passages formed in the first plate-shaped unit to flow out from the first plate-shaped unit (for example, see Patent Literature 1).